One insider says that Nordegren, 34, originally wanted to get to know Vonn, 29, because she knew the Olympic gold medalist would be around her children a lot. (The Swedish model and her pro golfer ex-husband, 38, have two kids together, daughter Sam, 6, and son Charlie, 5.)

"After meeting her, she found she actually liked her," the source says of Nordegren, who finalized her divorce from Woods in 2010, after it was famously revealed that he had cheated on her with over a dozen women.

"You'd think it would be weird, but Elin loves Lindsey and they talk all the time," the source tells Us. "Elin likes that Lindsey is a strong woman."

The source adds that the whole group recently went on vacation together, and that the fellow blondes occasionally took off on their own to grab drinks together, while Woods stayed with the kids. "Lindsey is really good for Tiger. She's strong, opinionated, and keeps him in line," the source explains. "Elin found that they are very similar and have a lot in common. They laugh and talk like they have been girlfriends forever."

Vonn and the golf pro went public with their romance back in March 2013, months after they were first linked. "We're athletes, so I guess we have something in common there. We met at his charity event in Vegas, Tiger Jam, and, yeah, we were friends for a long time," she told David Letterman in November of how their relationship evolved. "I don't know…we just kind of relate really well to one another."